1. Field of the Invention
The present invention relates to a klystron tuning mechanism, and more specifically to a high power klystron tuning mechanism for altering the high frequency power.
2. Description of the Prior Art
A high power klystron includes an electron gun for releasing electrons therefrom and thereby forming an electron beam, a RF section for interaction between the electron beam and the high frequency power, a collector for collecting the electrons, and a focusing unit for focusing the electron beam. The RF section includes cavity resonators, tuners for varying resonance frequencies of the cavity resonators, respectively, and a tuning mechanism for connecting and supporting the tuners. In case the high frequency power to be amplified is desired to be varied, it is necessary in the high power klystron to adjust a plurality of resonance frequencies of the cavity resonators to proper ones while observing frequency characteristics thereof on all such occasions. This causes inconvenience in its handling and operation as, compared with a travelling tube which is to amplify microwaves like the foregoing high power klystron.
To eliminate such inconvenience in the operation there is available a high power klystron including a tuning function which possesses a preset function in which it becomes possible at a previously set specific frequency to obtain easily a predetermined band width by carrying out only channel switching operation without performing any additional adjustment work. A prior art high power klystron including such a preset function as described above is arranged as illustrated in FIG. 1 for example. More specifically, the RF section of the high power klystron comprises a plurality of cavity resonators 1, tuners 2 of the same number as that of the cavity resonators wherein the cavity resonators 1 are varied in their volumes to change their resonance frequencies, and bellows 3 connected to the tuners 2 and the cavity resonators 1, respectively, for enabling the tuners 2 to go into and out (slide) the cavity resonators 1 by their mechanical deformation while keeping a vacuum in the high power klystron.
A tuning mechanism 4, which is connected to the tuners 2 each serving as described above to alter the resonance frequencies of the cavity resonators 1, comprises a tuner supporting mechanism 5 for exerting on the tuners 2 a biasing force in the opposite direction to the side of a vacuum tube of the high power klystron along the shafts of the tuners 2 at all times with the aid of restoring force of springs 8, a preset part 7 including means for moving parts on a preset plate 10 in parallel in response to a rotation of a pinion 11, the preset plate 10 being fixedly mounted on the RF section through the supporters 6 and allowing a plurality of sets of frequency setting screws 9 to be attached thereto, a tuning channel detector part 25 (refer to FIG. 2B) for detecting the fact that which frequency setting screw 9 is connected to the tuner 2, and a driving mechanism 13 for rendering a connection or a disconnection between the frequency setting screw 9 and the tuner shaft 12.
Herein, designated at 14 are bearings, 15 is a fixed plate, 16 is a locking shaft, 17 is a movable plate, 18 is a unlocking plate, 19 is a frequency alteration shaft, and 20 are locking plates.
Referring to FIGS. 2A and 2B, the tuning channel detector part 25 is illustrated in detail. In the lower part of the preset plate, 10, slits 21 are provided at locations corresponding to the frequency setting screws 9 (FIG. 2A). In order to permit the transmission of light through these slits 21, four successive photointerrupters 22 (each photointerrupter 22 comprises a light emitting diode 23 and a photodiode 24 as seen in FIG. 2B) are mounted on the preset plate 10 at the same pitch or interval as in the frequency setting screws 9. The photodiode 24 becomes conductive as light emanating from the light emitting diode 23 of the photointerrupter 22 reaches the photodiode 24 after passage through the slit 21, whilst the same photodiode 24 becomes non-conductive as the same light is interrupted. The slits 21 are disposed such that signals detected by the tuning channel detector part 25 are as listed in TABLE 1 for respective channels with the assumption of the conductive and non-conductive states of the photodiode 24 set to be 1 and 0.
TABLE 1 ______________________________________ Tuning Signals Detected by Tuning Channels Channel Detector Part ______________________________________ 1 1 0 1 1 2 0 1 1 0 3 1 1 0 1 4 1 0 1 0 5 0 1 0 0 6 1 0 0 0 ______________________________________
More specifically, with the arrangement illustrated in FIG. 2A (in the case of the tuning channel 1 in TABLE 1) a signal of 1011 is generated, and likewise once another frequency setting screw 9 is connected with the tuner 2 constituting part of the cavity resonator 1 by moving the preset plate 10, a signal corresponding to an associated tuning channel is generated from the tuning channel detector part 25. On the basis of the detected signal, it becomes possible to judge the fact that the associated klystron is set to which tuning channel.
A preset operation in the tuning mechanism, in which operation a predetermined band width is previously set for one tuning channel of the high power klystron through a set of the frequency setting screws 9 disposed along a drift tube of the cavity resonator, is performed as follows: First, an adjustment is performed with the aid of the frequency setting screws 9 such that the band width of the predetermined channel is yielded in the state of FIG. 1. In succession, the locking shaft 16 fixed through the bearing 14 to the fixing plate 15. The shaft is turned until the movable plate 17 makes contact with the unlocking plate 18. At this time, contacts between the tuner shafts 12 connected to the tuners 2 become disconnected. In this state, the frequency alteration shaft 19 is rotated to bring another frequency setting screw 9 into coincidence with the central axis of the timer shaft 12. At this location, the movable plate 17 is again moved until the movable plate strikes the locking plate 20 through the locking shaft 12. In this state, the degree of a projecting length of the frequency setting screw 9 is adjusted such that a predetermined band width characteristic is ensured in another tuning channel which is different from the foregoing tuning channel. With repetition of such adjustment a plurality of tuning channels of the high power klystron can be set previously.
In the tuning mechanism described above, any tuning channel is specified by a plurality of the slits 21 as illustrated in FIG. 2A, so that it is impossible to quickly and completely make the slits 21 and the photointerrupters 22 coincident with each other positionally, resulting in a difficulty of generated signals being slightly shifted in time. Accordingly, there might sometimes occur an inconvenience that upon alteration of a tuning channel, a signal of another tuning channel is sent from the tuning channel detector part. More specifically, an error might be produced in the signals detected by the tuning channel detection part listed in TABLE 1 that signals of other tuning channels are detected among the respective channels as listed in TABLE 2. Namely, there might be produced a possibility that erroneous detected signals with a pattern of TABLE 2 (signals indicated in parentheses) are issued.
TABLE 2 ______________________________________ Tuning Signals Detected by Tuning Channel Detector Channels Part ______________________________________ 6,4 1000 (0011, 1001, 0010, 0001), 1010 1 1011 6,5,4 1000 (00011, 1001, 0010, 0001), 0100, 1010 2 0110 6,5 1000, (0010), 1000 3 1101 6,5 1000, (0010), 0100 4 1010 6 1000, (0010) 5 0100 6 1000 ______________________________________
Channel alteration is thus recognized to have been completed at an incorrect location upon the alteration of a tuning channel, which impedes alteration to a tuning channel to be used.